A Publication of the Delta Stewardship Council

Panel Reviews Vernalis Adaptive Management Plan

The Delta Science Program recently convened an independent panel to review the Vernalis Adaptive Management Plan (VAMP) as part of a complete review of San Joaquin River flow objectives by the State Water Resources Control Board (SWRCB).

VAMP is a large-scale, decade-long experimental management program that was designed to protect juvenile Chinook salmon emigrating from the San Joaquin River through the Sacramento-San Joaquin Delta while providing scientific information for the SWRCB’s review and potential modification of the San Joaquin River flow objectives included in the Water Quality Control Plan (Bay-Delta Plan).

VAMP has been conducted annually since 2000 to evaluate the passage and survival of Chinook salmon smolts under a range of combinations of flows in the San Joaquin River and exports by the two major water projects in the Delta (Central Valley Project and State Water Project). When allowed, a physical (rock) barrier at the Head of Old River (HORB) has also been installed as part of the experiment. Several issues have affected VAMP implementation. A non-physical barrier has been installed in recent years, and may be installed in future years, due in part to Endangered Species Act restrictions (see December issue of Science News for the bubble barrier story). Flow and export combinations across the full range of VAMP targets have not occurred. An insufficient supply of juvenile salmon led to a switch from coded wire tags to acoustic tags in 2008.

The panel was charged to provide an independent review of the science generated by the VAMP and make recommendations for how this science should be used to inform changes to the Bay-Delta Plan. At the end of the March 2-3 review, the panel’s initial responses included:

The fish tagging studies have been well designed and implemented, but other aspects of the VAMP program such as the small range of exports examined and the recent move away from physical barrier installation are problematic.

There is some benefit for salmon remaining in the main channel of the San Joaquin River through the Delta.

Flow has a statistically significant effect on survival, but much of the benefit from increased flow appears to be contingent on there being a physical (rock) HORB.

The use of Chinook in studies as a surrogate for steelhead was not appropriate as steelhead and Chinook are too different in their life histories.

Continued use of coded wire tags will provide important information. Acoustic tag studies are a great new technology, but do not provide information about survival beyond the smolt stage.

Data gathered throughout a greater range in spring flows and more variable export rates are desirable, especially given historical and unimpaired flows/conditions in the San Joaquin River.

The very high rates of predation measured in 2009 when a nonphysical barrier was installed may not be the norm because of the very low flow conditions.

Additional years of acoustic tagging data are needed to evaluate predation and survival.

Future challenges for the VAMP participants include integration of new Endangered Species Act regulatory requirements into the existing SWRCB regulatory framework. The VAMP review panel is writing a report on their findings and will be submitting the report to the Delta Science Program. The final report will be posted on the Delta Stewardship Council web site and will be provided to the SWRCB for use in their process to develop new or revised flow objectives for the San Joaquin River.